(1) Field of the Invention
The present invention relates to an apparatus for folding sheet material, such as one or more paper sheets or the like, comprising a rotatable magazine holding the sheet material with portions thereof projecting beyond two parallel folding plates of the magazine, and folding elements arranged outside the magazine and bending the projecting sheet material portions about respective ones of parallel end edges of the folding plates upon rotation of the magazine.
(2) Description of the Prior Art
Such a folding apparatus has been used in a machine for folding mailing pieces in an envelope machine. Each mailing piece is first bent over a rear end edge of one of the folding plates before it is introduced with the resultant fold into the nip of a pair of pressure rolls which produce the desired pressed fold. In this known apparatus, the mailing piece is drawn between the folding plates by conveying rollers arranged in the magazine and passing through openings in the folding plates until they come to rest at the desired location of the mailing piece against the rear end edge of the folding plate. In this position, the mailing piece is engaged by the conveying rollers and the magazine is rotated not quite 180.degree. until the mailing piece portion at the rear folding plate edge comes to rest against a pressure roller resiliently mounted outside of the magazine and, upon further rotation of the magazine into the 180.degree. position, the pressure roller bends this mailing piece portion about the rear folding plate edge and presses the adjoining mailing piece portion against a guide roll affixed to the magazine. In this position, the folded mailing piece is transported forwardly out of the magazine and into the nip of the pair of pressure rolls by the conveying rollers, the pressure roller and the guide roll. The mailing piece leaves the machine after this single folding. For mailing pieces that must be folded several times, a series of such machines are arranged sequentially.
Other folding machines for providing zig-zag folds and various other types of folds for various paper sizes are also known. All known folding machines are designed for folding paper sheets of different sizes at a speed of 12,000 to 20,000 sheets/hour, with an automatic paper feed. The machines are technically quite complex, large and heavy. Particularly for the normal daily mailing pieces generated by small to medium-sized offices, up to 90% of which tend to be of a size DIN A 4 (about 8".times.12"), these machines are too large.